some plots so far

From: Marc Postman (postman@stsci.edu)
Date: Thu Jan 05 2006 - 08:57:32 PST

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    Saul,

    Here are two examples of relative surface densities of galaxies as a
    function of their color, cluster membership, and elliptical morphology.
    While it is true that the total number of cluster ellipticals is often
    not that much greater than the total number of field ellipticals for a
    given ACS pointing, the cluster ellipticals are all at the SAME
    redshift whereas the field ellipticals span a large redshift range.
    Therefore if one wants to probe a given redshift, using a cluster is by
    far the better way to go. I think we can quantify this as well in a
    separate plot. For example, in MS1054 there are 61 field ellipticals
    and 81 cluster ellipticals with i <= 23.5 in the same ACS pointing. In
    RXJ1252-29, there are 53 field ellipticals and 53 cluster ellipticals
    with z <= 24.5 in the same ACS mosaic. But the 53 cluster ellipticals
    are obviously all at z=1.24 (modulo errors in photo-z) whereas the
    field ellipticals span a much broader range and largely sample lower
    redshifts.

    I don't think it will be easy to generate similar figs for our other
    clusters in time for the proposal deadline, however. A lot of work is
    needed to generate photo-z info and morphological info.

    Marc






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